The present invention pertains generally to infrared sensitive systems, and more particularly to an infrared system which maintains an inventory of persons within a certain zone to control electronic equipment.
It is generally known to provide a detector unit which includes an infrared light source and a lens for focusing infrared radiation onto an infrared detecting element as is described in U.S. Pat. No. 4,275,303, and in U.S. Pat. No. 4,510,488 which describes a passive infrared intrusion detector configured to resemble an electrical wall outlet.
Infrared detection systems such as described in U.S. Pat. No. 4,612,442 to Toshimichi includes an alarm output circuit driven in response to the output generated from a combined counter and comparator. The counter counts pulses to generate an alarm when the number of pulses counted coincides with a preset value. The first input pulse triggers a timer circuit to generate a positive output during a predetermined time interval and controls the count time of the counter.
Certain limitations are implicit in the passive infrared system of Toshimichi. First, the system functions only to actuate an alarm signal. Second, when the pulse generator transmits a low signal, it causes the counter to reset to a base value. Third, there is no provision to deactivate the alarm signal in a certain zone when an intruder leaves the zone.
Consequently, a need exists for improvements in infrared detection systems used to control electronic equipment in response both to the entry into and exit from a certain zone, whereby an electronic device such as a light member, an audio system, a video system and the like, activates when a person enters a certain zone, and deactivates when the last person exits from the certain zone.